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Escape artist's gambit
rogue attack 17

Prerequisite: Acrobatics trained.

Target: one creature

Attack: Dexterity vs. AC

Hit: "2[W] + Dexterity modifier damage, and you can shift 1 square. If you are immobilized, slowed, or both, those conditions end before you shift, and you automatically escape if you are grabbed."
Artful Dodger: You can instead shift a number of squares equal to 1 + your Dexterity modifier.[MP:82]

Escape artist's gambit is an encounter power available to rogues at 17th level.